Casual Fixation Disparity Testing: Comparing The Saladin Card To The Sheedy Disparometer.

Background: The purpose of this study was to determine if the Saladin Card and Sheedy
Disparometer would result in comparable FD measurements under casual testing
parameters as normally used in a clinical setting. Methods: 32 young adults age 19 to 38, with best corrected near visual acuity in place resulting in 20/20 vision were tested to measure fixation disparity with the Saladin Card and the Sheedy Disparometer through prism loads of 0, 4BI and 4BO. Results: The Pearson r correlation coefficient comparing the Saladin Card and the Disparometer show a statistically significant correlation with r=.50 for 0, r=.68 for 4BI and r=.45 for 4BO. Also evident with this study is a large amount of variability in the Disparometer readings and the trend toward smaller magnitude readings with the Saladin Card. Conclusion: Under casual testing conditions, the FD measurements done by the two instruments are correlated and likely related. The results though can be contaminated by the large amount of variability in Disparometer readings. Though the two testing methods correlate well, the smaller magnitude of the FD results from the Saladin Card can make using the same norms questionable.